The present invention relates to a plating jig for holding a flexible pipe material having a slit in the lengthwise direction thereof and a plating method using the plating jig and, in particular, relates to a plating jig and a plating method adapted to the case where electroless plating is applied to a long-size corrugated tube formed of a resin material.
In recent years, electronic application to controllers has been developed in the field of cars, machine tools, office machines, etc. Measures counter to electromagnetic wave noise in these electronic appliances have become an important problem. Such electronic appliances require shielding measures for shielding internal conductors of wirings from external electric field because wirings connected to the electronic appliances are apt to absorb electromagnetic wave noise. The shielding of the internal conductors is performed by grounding external conductors covering the internal conductors. One of the external conductors used in this occasion is a shielded-plating corrugated tube obtained by applying plating to a bellows-like pipe material (corrugated tube) having flexibility and formed of a resin material. The shielded-plating corrugated tube is formed so as to have a shielding effect by applying plating to a tube used originally as a wiring protecting material. In the shielded-plating corrugated tube, a slit for inserting wiring therein is formed in the lengthwise direction in the same manner as in the conventional corrugated tube.
For plating the shielded-plating corrugated tube, an electroless plating method is used because the corrugated tube (to be plated) as a base is an electrically insulating material. In the electroless plating method, a material (to be plated) with a catalyst spread on the surface thereof is put into a bath containing a metal ion and a reducing agent, so that a metal coating is formed on the surface of the material (to be plated) by a catalytic reaction. Such electroless plating is classified by plating equipment into a hang-plating method (also called a rack type plating method), a barrel plating method, etc.
In the hang-plating method, as shown in FIGS. 19 and 20, a roll of long-size corrugated tube 3 is put into a resin-coated cage 1 and then a set of the corrugated tube 3 and the cage 1 is put into a plating tank 7 in which a plating solution 5 is stored. In another method, as shown in FIG. 21, short-cut corrugated tubes 3 may be put into a plating tank 7 while hung by a rack 9.
On the other hand, in the barrel plating method, as shown in FIG. 22, a roll of corrugated tube 3 put into a cylindrical wire net cage 11 is put into a plating tank 7, so that plating is performed while rotating or swinging the wire net cage 11.
In the plating method shown in FIG. 20, however, the slit formed in the lengthwise direction of the corrugated tube 3 is not disposed in a predetermined direction. Accordingly, in a portion in which the slit 3a is disposed downward as shown in FIG. 23(A), bubbles 13 of air remaining in the corrugated tube 3 without being discharged from the corrugated tube 3 or hydrogen gas or the like, generated in the plating solution remain in the inside in the form of a bubble reservoir, so that the portion does not touch the plating solution. As a result, there arises a problem that portions which are not plated may be generated. Further, in a portion in which the slit 3a is disposed upward as shown in FIG. 23(B), when the corrugated tube 3 is pulled up from the plating tank, some plating solution remains in the bottom portion, that is, so-called bailing of the plating solution occurs. As a result, there arises a problem that the remaining plating solution is mixed with the next plating solution so that deterioration of the plating solution makes proper plating impossible. If exchange of the plating solution to a new one is performed frequently in order to prevent the deterioration of the plating solution, production costs increase.
Further, in the plating method shown in FIG. 21, there arises a problem that not only the commercial value thereof is reduced because the corrugated tube 3 is cut into a short length, but also production costs are increased because large scale processing cannot be performed.
Further, in the plating method shown in FIG. 22, the slit 3a is not disposed in a predetermined direction in the same manner as in the method shown in FIG. 20. Accordingly, there arises a problem that not only plating failure due to the bubble reservoir and deterioration of the plating solution due to the bailing of the plating solution occur but also corrugated tubes 3 are apt to touch each other so that adhesion of plating in the contact portion is lowered.